When doing a query like this:
SELECT id FROM users WHERE (users.id IN (899,1084,1095,100,2424,2429,2420))

the order of the returned records is undefined. To force the query to return the records in a given order, you have to add ORDER BY FIELD(id, 899, 1084, ...)

So the query looks like this:
SELECT id FROM users WHERE (users.id IN (899,1084,1095,100,2424,2429,2420)) ORDER BY FIELD(id,899,1084,1095,100,2424,2429,2420);

An alternative to this technique is using VCR. VCR allows you to record and replay real HTTP responses, saving you the effort to stub out request/response cycles in close details. If your tests do require close inspection of requests and responses, Webmock is still the way.

WebMock is an alternative to FakeWeb when testing code that uses the network. You sh...

Open the configuration file:

gksudo gedit /usr/share/vte/termcap/xterm

Find a line like this:

:co#80:it#8:li#24:\

Change the first and last number to your desired columns and rows:

:co#160:it#8:li#40:\

Save your changes and close all open terminals. New terminals should now open with the new size.

In a nutshell: to avoid your shell character set from messing with imports, use -r to export and SOURCE when importing.

Dumping safely

# Do not do this, since it might screw up encoding
mysqldump -uroot -p database > utf8.dump # this is bad

Better do:

mysqldump -uroot -p database -r utf8.dump

Note that when your MySQL server is not set to UTF-8 you need to do mysqldump --default-character-set=latin1 (!) to get a correctly e...

First do

ALTER DATABASE database_name CHARACTER SET "utf8";
ALTER DATABASE database_name COLLATE "utf8_unicode_ci";

After that, for each table:

ALTER TABLE table_name DEFAULT CHARACTER SET "utf8" COLLATE "utf8_unicode_ci";

This just changes the default character set / collation for each table. To convert them, you need:

ALTER TABLE tablename CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

home_run is an implementation of ruby’s Date/DateTime classes in C, with much better performance (20-200x) than the version in the standard library, while being almost completely compatible.

Ancestry is a gem/plugin that allows the records of a Ruby on Rails ActiveRecord model to be organised as a tree structure (or hierarchy). It uses a single, intuitively formatted database column, using a variation on the materialised path pattern. It exposes all the standard tree structure relations (ancestors, parent, root, children, siblings, descendants) and all of them can be fetched in a single sql query. Additional features are STI support, named_scopes, depth caching, depth constraints, easy migration from older plugins/gems, integrit...

This may be awkward to set up, but will work once you're done.

Fun facts:

• In case of a connection loss the slave will try to reconnect to the master server and resume replication for the next 24 hours
• If you want to use your slave as a "real" MySQL server, you basically need to switch off replication (STOP SLAVE; RESET SLAVE; and reset your my.cnf) and restart the MySQL daemon.

Master server configuration

• Create replication user

  In the MySQL shell:

  CREATE USER 'replicator'@'%' IDENTI...
  

Unless all MySQL server defaults are set to UTF-8, mysqldump encodes UTF-8 characters incorrectly and only outputs correct UTF-8 when you switch to Latin 1 (!). Also you need to setup charset and collation manually for each new database.

To prevent this, make sure your /etc/mysql/my.cnf looks like this:

[mysqld]
default-character-set = utf8mb4
collation-server = utf8mb4_unicode_ci

[mysql]
default-character-set=utf8mb4

After that do

sudo /etc/init.d/mysql restart

To test concurrent code, you will need to run multiple threads. Unfortunately, when you use blocking system calls (e.g. locks on the database), Ruby 1.8 threads won't work because system calls will block the whole interpreter.

Luckily you can use processes instead. fork spins off a new process, IO.pipe sends messages between processes, Process.exit! kills the current process. You will need to take care of ActiveRecord database connections.

Here is a full-fledged example:

describe Lock, '.acquire' do

  before :each do
  ...

Install gem and plugin

sudo gem install parallel
script/plugin install git://github.com/grosser/parallel_tests.git

Adapt config/database.yml

test:
  database: xxx_test<%= ENV['TEST_ENV_NUMBER'] %>

Create test databases

script/dbconsole -p
CREATE DATABASE `xxx_test2`;
...

Generate RSpec files

script/generate rspec

(you'll probably only let it overwrite files in script/)

Prepare test databases...

This is about converting Haml to ERB and not the other way round which you probably want!

This process can not be automated 100%, but you can still save time.

First do

script/plugin install http://github.com/cgoddard/haml2erb.git

Then in the console type

hamls = Dir["app/views/**/*.haml"] - ['app/views/layouts/screen.html.haml'];
hamls.each do |haml| 
  puts haml
  erb = haml.sub(/\.haml$/, '.erb')
  File.open(erb, 'w') do |file| 
    file.write Haml2Erb.convert(File.read(haml)) 
  end
end

After th...

sudo gem install zip
git clone git://github.com/rtomayko/date-performance.git
cd date-performance
rake package:build
cd dist
sudo gem install --no-ri --no-rdoc date-performance-0.4.7.gem

ActsAsSolr::Post.execute(Solr::Request::Delete.new(:query => "#{Location.solr_configuration[:type_field]}:#{ModelClass}"))
ActsAsSolr::Post.execute(Solr::Request::Commit.new)

This can happen during development when classes without automatic reloading are pointing to classes with automatic reloading. E.g. some class in lib is calling Model.static_method.

Workaround A

Stop referencing autoloaded classes from static files. If you can't, see workaround B and C.

Workaround B

Make sure the offending file (the one referencing the autoloaded class) is autoloaded, too. You may do this:

# config/application.rb

  config.paths.add 'offending/file/parent/directory', eager_load: true

Workaroun...

log/*
tmp/*
storage/*
db/*.sqlite3
db/schema.rb
db/structure.sql
public/system
.project
.idea/
public/javascripts/all*
public/stylesheets/all*
public/stylesheets/*.css
config/database.yml
*~
*#*
.#*
.DS_Store
webrat-*.html
capybara-*.html
rerun.txt
coverage.data
coverage/*
dump_for_download.dump
.~lock.*
.*.swp
C:\\nppdf32Log\\debuglog.txt

1. before transition
2. before validation
3. after validation
4. before save
5. after save
6. after transition

Aborting the callback chain

See Cancel the ActiveRecord callback chain.

You are getting when connecting via SSH or deploying with Capistrano (which uses SSH):

Too many authentication failures for username

This is caused by having too many SSH keys added to your keyring or ssh-agent. Your ssh-agent will throw all keys against a server until one matches. Most servers will deny access after 5 attempts.

This issue might come and go as the order of the active SSH keys in your ssh-agent changes.

Quick fix

Have less keys. Up to 5 keys are fine when the SSHD you're connecting to is using the default ...

When you include a non-existing Javascript file, you probably won't notice it during development. But with caching active (on production or staging) Rails will write an empty all.js file without complaining.

Gem to provide nice looking urls ("/blog/the-greatest-bug-i-never-fixed"). If you don't need anything too special (like i18n for the urls) it works as a drop-in-replacement. It basically overwrites #to_param to return the slug, and .find to search by the slug.

Make sure, everywhere you build paths, you use model_path(:id => model) instead of model_path(:id => model.id). You also need to adapt all code using something like .find_by_id. The regular .find is fine.

See the github README for installation instructions.

Don't forget ...

YSlow analyzes web pages and tells you why they're slow based on the rules for high performance web sites. YSlow is a Firefox add-on integrated with the popular Firebug web development tool.

Web performance expert Nicole Sullivan discusses a set of best practices in the creation of supremely fast, visually impactful web sites.

A while back, I had a requirement to persist a record of which email addresses were sent an email through the system. I expected to find callback support for ActionMailer, but was surprised to find that it didn't exist.

Squirrel is an enhancement for ActiveRecord’s find method that allows programmers to query the database using a more Rubyish syntax.